Such a pressure sensor includes a measuring membrane, or diaphragm, at least one platform and a capacitive transducer having at least a first pressure dependent capacitance and a second pressure dependent capacitance, wherein the measuring membrane divides a volume pressure-tightly into a first volume portion and second volume portion, wherein the second volume portion is enclosed in a measuring chamber between the measuring membrane and the platform, wherein a deflection of the measuring membrane depends on a pressure measurement variable p, which is a difference between a first pressure p1 in the first volume portion and a second pressure p2 in the second volume portion in the measuring chamber, wherein the first capacitance and the second capacitance are measured, in each case, between an electrode on the measuring membrane and a counter electrode having an essentially pressure independent position, wherein a respectively current value of the pressure measurement variable p is ascertained as a function of the first capacitance and of the second capacitance.
The exact relationship between the pressure measurement variable p and the two capacitances depends especially on the positions of the electrodes in relationship to the measuring membrane and the bending characteristic of the measuring membrane. To the extent that these boundary conditions are fixed by the manner of construction, the pressure measurement variable p can be determined as a function of the current measured values of the capacitances and, in given cases, other disturbance variables, such as the temperature. This assumes, however, that the construction dependent characteristics of the pressure sensor, which influence the transfer functions, are sufficiently stable, and that the pressure sensor especially is at least sufficiently in thermal equilibrium that the characteristics do not deviate too much from equilibrium conditions.
Disclosed in the European publication EP 2 189 774 A1 is a method for compensating rapid temperature changes, which rests on features including that for measured values of the measured capacitance Cp (there designated Cm) the measured values of the reference capacitance Cr are compared with expected values of the reference capacitance Cr, which follow from the measured values of the measured capacitance Cp, and wherein a temperature jump is detected, when the measured value of the reference capacitance lies outside a tolerance range around an expected value, and wherein then for the pressure measured value a correction function is ascertained, which specifically should correct the influence of the temperature jump on the pressure measurement value. In the said publication, it is thus taught to interpret changes of the transfer functions as results of temperature jumps and accordingly in the evaluation to compensate the capacitances model-based. Although this approach has its merits, it errs to the extent that a change of the transfer function can also have other causes, for example, a permanent change in, especially damage to, the measuring cell. This thus has the danger that such a change in the measuring cell remains undetected, and, indeed, with the consequence that one thinks a correct pressure measurement is being made, while, in fact, the resulting measured values are completely wrong.